The Bintiva large wobble cushion, is an important strengthening tool to be used by adults and children. The simple act of sitting on the disc activates core abdominal and trunk muscles. Flexor and extensor muscles work in tandem to keep your balance on the disc while continuously strengthening and toning. Through these small, continuous motions that you are making, deep core muscles are constantly stimulated and enhanced. It is very important to maintain an upright posture while seated on the disc. It is however, not meant for sitting only. You can actually stand, kneel, and do all sorts of exercises on it, thereby increasing the benefits of those exercise routines. This larger cushion is 37 cm/ 14.5 inches and is smooth on one side and has round nubs on the other.